1. FIELD OF THE INVENTION
The present invention relates to a device and method for softening atherosclerotic plaque buildup in a blood vessel in order to restore necessary blood flow. The device includes a catheter with a tip member having heating means therein for applying heat directly to an atherosclerotic plaque area within a blood vessel whereby the heat softens the fatty material of the plaque.
2. DESCRIPTION OF THE PRIOR ART
Heretofore, various body insertable devices with heat generation means, such as a heated tip catheter, have been proposed for delivering heat to internal organs, cavities or vessels of a body.
Such devices have also been used as temperature measuring devices, and for heating fluid transferred to or from the body.
Examples of some of the previously proposed devices are disclosed in the following patents:
______________________________________ U.S. PAT. NO. PATENTEE ______________________________________ 623,022 Johnson 1,677,642 Kirk 3,798,967 Gieles et al 4,038,519 Foucras 4,217,910 Khalil 4,227,535 Connor 4,240,441 Khalil ______________________________________
The Johnson U.S. Pat. No. 623,022 dicloses a catheter which is adapted for insertion into a body cavity and which is allegedly capable of delivering an electric current to the body. The electric current was believed to have some curative powers, and no reference is made in this patent to heat generation. The catheter can be used for delivering fluid into the body and the electric current allegedly flows from the catheter through the fluid into the body.
The Kirk U.S. Pat. No. 1,677,642 discloses a double barrelled catheter wherein one barrel delivers medication and the other barrel delivers heat to any internal cavity, organ or tissue. The barrel which delivers heat is provided with an electrical heater with suitable number of wound conductor turns to provide a desired resistance in conductors which extend through an attaching socket for connection to a source of current.
The Gieles et al U.S. Pat. No. 3,798,967 discloses both a method and a probe for measuring blood flow in a blood vessel. The probe delivers high frequency electromagnetic energy to the blood and this energy is then converted to heat in the blood itself as the blood flows through an energy field formed within a "cage" at the tip of the probe. The heating, however, is indirect in that the probe generates heat in the surrounding blood by creating an electromagnetic field and is only used for flow measuring purposes.
The Foucras U.S. Pat. No. 4,038,519 discloses a flexible heating tube for medical use which is heated by electric resistance wires embedded in the wall of the tube in a helical pattern about the lumen of the tube. The tube is used for the transfer of heated body fluids to and from the body and the heating elements are used to maintain a proper temperature of the fluids.
The Khalil U.S. Pat. Nos. 4,217,910 and 4,240,441 disclose a thermo-dilution catheter having at its distal end a high frequency heating coil, a heat measuring thermocouple and a resistance thermometer which are used for measuring the flow of blood at the catheter distal end in either a jugular vein, a left ventricle, or a carotid artery. The catheter operates on a thermo-dilution principle. In use, the heating coil heats the blood to one temperature at one location and the drop in temperature measured at another location downstream is indicative of the rate of flow of the blood.
The Connor U.S. Pat. No. 4,227,535 discloses a proctological device for therapeutically treating hemorrhoids. The device includes a heating element which is placed in contact with the hemorrhoid to cauterize it. The heating element includes an internal electric resistor within the device for generating heat in response to the application of electrical energy. A temperature transducer is also situated within the device for sensing the temperature of the device in the anal canal. The electrical resistor of the heating element is a helically wound coil on a cylindrical insulative heating core mounted within a cylindrical envelope having an exterior heat transfer surface. The cylindrical envelope has a length sufficient to extend totally from the anus through the anal canal to the rectum.
As will be described in greater detail hereinafter, the device and method for softening atherosclerotic plaques of the present invention differs from the devices and methods previously proposed by providing a catheter which is sized to be received in a blood vessel and which has a heat transfer surface localized in a tip member mounted to the distal end of the catheter. The catheter is manipulatable into and through the lumen of a blood vessel and can be positioned therein proximate atherosclerotic plaque buildup in the blood vessel. Heat is then generated and supplied to the atherosclerotic plaques for a predetermined period of time to resolve the plaque.
Still further, in one preferred embodiment of the present invention, there is provided a tubular tip member open at the distal end and communicating at the proximate end with at least one port in the wall of the device. The tubular tip member and port or ports permit the flow of blood through and around the tip member. The tubular tip member and port permit treatment of plaque buildup for an extended period of time without interrupting the flow of blood through the vessel in the area of the plaque buildup.